Layer 4 of the OSI model corresponds to which layer of the DoD model?

In the context of the OSI (Open Systems Interconnection) model and the DoD (Department of Defense) model, Layer 4 of the OSI model is indeed equivalent to Layer 3 of the DoD model, which is known as the Host-to-Host layer.

The OSI model's Layer 4 is responsible for ensuring reliable data transmission between host devices. This involves the establishment, management, and termination of connections, flow control, and error recovery. Protocols at this layer, such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol), facilitate this process by managing how much data is sent and through what mechanisms.

The DoD model simplifies the OSI framework into four layers, where the Host-to-Host layer corresponds to aspects of transport and data delivery. This layer deals specifically with the communication between devices over a network, fulfilling responsibilities similar to those outlined in the OSI model's Layer 4. By maintaining this relationship, the DoD model ensures a clear understanding of how data moves across networks, aligning closely with the functionalities of transport protocols in the OSI framework.